diff --git a/python/pyproject.toml b/python/pyproject.toml
index 9be8cb833..0d4c89240 100755
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -30,7 +30,7 @@ dependencies = [
   "easydict",  # Required by remote model code (e.g. DeepSeek-OCR) loaded via trust_remote_code; validated by transformers 5.4+ check_imports
   "einops",
   "fastapi",
-  "flash-attn-4>=4.0.0b9",
+  "flash-attn-4==4.0.0b15",
   "flashinfer_cubin==0.6.12",
   "flashinfer_python[cu13]==0.6.12", # keep it aligned with jit-cache version in Dockerfile
   "gguf",